diff --git a/IMPLEMENTATION_PLAN.md b/IMPLEMENTATION_PLAN.md
index 77af88b..a275e70 100644
--- a/IMPLEMENTATION_PLAN.md
+++ b/IMPLEMENTATION_PLAN.md
@@ -4,7 +4,7 @@ This file is maintained by Ralph. Run `./ralph-sandbox.sh plan 3` to generate ta
 
 ## Current State Summary
 
-### Overall Status: 841 tests passing across 44 test files
+### Overall Status: 849 tests passing across 44 test files
 
 ### Library Implementation
 | File | Status | Gap Analysis |
@@ -113,7 +113,7 @@ This file is maintained by Ralph. Run `./ralph-sandbox.sh plan 3` to generate ta
 | `src/app/settings/page.test.tsx` | **EXISTS** - 34 tests (form rendering, validation, submission, accessibility, logout functionality) |
 | `src/app/api/auth/logout/route.test.ts` | **EXISTS** - 5 tests (cookie clearing, success response, error handling) |
 | `src/app/settings/garmin/page.test.tsx` | **EXISTS** - 27 tests (connection status, token management) |
-| `src/components/dashboard/decision-card.test.tsx` | **EXISTS** - 11 tests (rendering, status icons, styling) |
+| `src/components/dashboard/decision-card.test.tsx` | **EXISTS** - 19 tests (rendering, status icons, styling, color-coded backgrounds) |
 | `src/components/dashboard/data-panel.test.tsx` | **EXISTS** - 18 tests (biometrics display, null handling, styling) |
 | `src/components/dashboard/nutrition-panel.test.tsx` | **EXISTS** - 12 tests (seeds, carbs, keto guidance) |
 | `src/components/dashboard/override-toggles.test.tsx` | **EXISTS** - 18 tests (toggle states, callbacks, styling) |
@@ -702,18 +702,18 @@ Testing, error handling, and refinements.
 ### P3.11: Missing Component Tests ✅ COMPLETE
 - [x] Add unit tests for untested components
 - **Components Tested (5 total):**
-  - `src/components/dashboard/decision-card.tsx` - 11 tests for rendering decision status, icon, reason, styling
+  - `src/components/dashboard/decision-card.tsx` - 19 tests for rendering decision status, icon, reason, styling, color-coded backgrounds
   - `src/components/dashboard/data-panel.tsx` - 18 tests for biometrics display (BB, HRV, intensity), null handling, styling
   - `src/components/dashboard/nutrition-panel.tsx` - 12 tests for seeds, carbs, keto guidance display
   - `src/components/dashboard/override-toggles.tsx` - 18 tests for toggle states, callbacks, styling
   - `src/components/calendar/day-cell.tsx` - 23 tests for phase coloring, today highlighting, click handling
 - **Test Files Created:**
-  - `src/components/dashboard/decision-card.test.tsx` - 11 tests
+  - `src/components/dashboard/decision-card.test.tsx` - 19 tests
   - `src/components/dashboard/data-panel.test.tsx` - 18 tests
   - `src/components/dashboard/nutrition-panel.test.tsx` - 12 tests
   - `src/components/dashboard/override-toggles.test.tsx` - 18 tests
   - `src/components/calendar/day-cell.test.tsx` - 23 tests
-- **Total Tests Added:** 82 tests across 5 files
+- **Total Tests Added:** 90 tests across 5 files
 - **Why:** Component isolation ensures UI correctness and prevents regressions
 
 ---
@@ -902,7 +902,7 @@ P4.* UX Polish ────────> After core functionality complete
 - [x] **metrics.ts** - Complete with 18 tests (metrics collection, counters, gauges, histograms, Prometheus format) (P2.16)
 
 ### Components
-- [x] **DecisionCard** - Displays decision status, icon, and reason
+- [x] **DecisionCard** - Displays decision status, icon, reason with color-coded backgrounds (RED/YELLOW/GREEN per status)
 - [x] **DataPanel** - Shows body battery, HRV, intensity data
 - [x] **NutritionPanel** - Shows seeds, carbs, keto guidance
 - [x] **OverrideToggles** - Toggle buttons for flare/stress/sleep/pms
@@ -952,7 +952,7 @@ P4.* UX Polish ────────> After core functionality complete
 - [x] **P3.7: Error Handling Improvements** - Replaced console.error with structured pino logger across API routes, added key event logging (Period logged, Override toggled, Decision calculated, Auth failure), 3 new tests in auth-middleware.test.ts
 - [x] **P3.8: Loading States** - Complete with skeleton components (DecisionCardSkeleton, DataPanelSkeleton, NutritionPanelSkeleton, MiniCalendarSkeleton, OverrideTogglesSkeleton, CycleInfoSkeleton, DashboardSkeleton), 29 tests in skeletons.test.tsx; loading.tsx files for all routes (dashboard, calendar, history, plan, settings); shimmer animations matching spec requirements
 - [x] **P3.9: Token Expiration Warnings** - Complete with 10 new tests in email.test.ts, 10 new tests in garmin-sync/route.test.ts; sends warnings at 14 and 7 days before expiry
-- [x] **P3.11: Missing Component Tests** - Complete with 82 tests across 5 component test files (DecisionCard: 11, DataPanel: 18, NutritionPanel: 12, OverrideToggles: 18, DayCell: 23)
+- [x] **P3.11: Missing Component Tests** - Complete with 90 tests across 5 component test files (DecisionCard: 19, DataPanel: 18, NutritionPanel: 12, OverrideToggles: 18, DayCell: 23)
 
 ### P4: UX Polish and Accessibility
 - [x] **P4.1: Dashboard Onboarding Banners** - Complete with OnboardingBanner component (16 tests), dashboard integration (5 new tests)
@@ -977,7 +977,7 @@ Analysis of all specs vs implementation revealed these gaps:
 | Garmin sync structured logging | observability.md | **COMPLETE** | Added sync start/complete/failure logging |
 | Email sent/failed logging | observability.md | **COMPLETE** | Email events now logged (info for success, error for failure) with structured data (userId, emailType, success) |
 | Period history UI | cycle-tracking.md | **PENDING** | UI for viewing/editing past periods |
-| Dashboard color-coded backgrounds | dashboard.md | **PENDING** | Phase-based background colors |
+| Dashboard color-coded backgrounds | dashboard.md | **COMPLETE** | DecisionCard shows RED/YELLOW/GREEN backgrounds per status (8 new tests) |
 | Toast notifications | dashboard.md | **PENDING** | Success/error toasts for user actions |
 | CI pipeline | testing.md | **PENDING** | GitHub Actions for test/lint/build |
 
diff --git a/src/components/dashboard/decision-card.test.tsx b/src/components/dashboard/decision-card.test.tsx
index b32a45e..4f287f6 100644
--- a/src/components/dashboard/decision-card.test.tsx
+++ b/src/components/dashboard/decision-card.test.tsx
@@ -122,6 +122,112 @@ describe("DecisionCard", () => {
     });
   });
 
+  describe("color-coded backgrounds", () => {
+    it("renders REST with red background", () => {
+      const decision: Decision = {
+        status: "REST",
+        reason: "Recovery day",
+        icon: "🛌",
+      };
+
+      const { container } = render(<DecisionCard decision={decision} />);
+
+      const card = container.firstChild as HTMLElement;
+      expect(card).toHaveClass("bg-red-100", "border-red-300");
+    });
+
+    it("renders GENTLE with yellow background", () => {
+      const decision: Decision = {
+        status: "GENTLE",
+        reason: "Light movement",
+        icon: "🧘",
+      };
+
+      const { container } = render(<DecisionCard decision={decision} />);
+
+      const card = container.firstChild as HTMLElement;
+      expect(card).toHaveClass("bg-yellow-100", "border-yellow-300");
+    });
+
+    it("renders LIGHT with yellow background", () => {
+      const decision: Decision = {
+        status: "LIGHT",
+        reason: "Moderate intensity",
+        icon: "🚶",
+      };
+
+      const { container } = render(<DecisionCard decision={decision} />);
+
+      const card = container.firstChild as HTMLElement;
+      expect(card).toHaveClass("bg-yellow-100", "border-yellow-300");
+    });
+
+    it("renders REDUCED with yellow background", () => {
+      const decision: Decision = {
+        status: "REDUCED",
+        reason: "Lower intensity",
+        icon: "⬇️",
+      };
+
+      const { container } = render(<DecisionCard decision={decision} />);
+
+      const card = container.firstChild as HTMLElement;
+      expect(card).toHaveClass("bg-yellow-100", "border-yellow-300");
+    });
+
+    it("renders TRAIN with green background", () => {
+      const decision: Decision = {
+        status: "TRAIN",
+        reason: "Full intensity approved",
+        icon: "🏃",
+      };
+
+      const { container } = render(<DecisionCard decision={decision} />);
+
+      const card = container.firstChild as HTMLElement;
+      expect(card).toHaveClass("bg-green-100", "border-green-300");
+    });
+
+    it("renders reason with appropriate text color for REST", () => {
+      const decision: Decision = {
+        status: "REST",
+        reason: "Rest message",
+        icon: "🛌",
+      };
+
+      render(<DecisionCard decision={decision} />);
+
+      const reason = screen.getByText("Rest message");
+      expect(reason).toHaveClass("text-red-700");
+    });
+
+    it("renders reason with appropriate text color for GENTLE", () => {
+      const decision: Decision = {
+        status: "GENTLE",
+        reason: "Gentle message",
+        icon: "🧘",
+      };
+
+      render(<DecisionCard decision={decision} />);
+
+      const reason = screen.getByText("Gentle message");
+      expect(reason).toHaveClass("text-yellow-700");
+    });
+
+    it("renders reason with appropriate text color for TRAIN", () => {
+      const decision: Decision = {
+        status: "TRAIN",
+        reason: "Train message",
+        icon: "🏃",
+      };
+
+      render(<DecisionCard decision={decision} />);
+
+      const reason = screen.getByText("Train message");
+      expect(reason).toHaveClass("text-green-700");
+    });
+  });
+
   describe("styling", () => {
     it("renders within a bordered container", () => {
       const decision: Decision = {
@@ -133,7 +239,7 @@ describe("DecisionCard", () => {
       const { container } = render(<DecisionCard decision={decision} />);
 
       const card = container.firstChild as HTMLElement;
-      expect(card).toHaveClass("rounded-lg", "border", "p-6");
+      expect(card).toHaveClass("rounded-lg", "p-6");
     });
 
     it("renders status as bold heading", () => {
@@ -150,17 +256,17 @@ describe("DecisionCard", () => {
       expect(heading).toHaveClass("font-bold");
     });
 
-    it("renders reason with muted color", () => {
+    it("renders reason with status-specific color", () => {
       const decision: Decision = {
         status: "REST",
-        reason: "Muted reason text",
+        reason: "Reason with status color",
         icon: "🛌",
       };
 
       render(<DecisionCard decision={decision} />);
 
-      const reason = screen.getByText("Muted reason text");
-      expect(reason).toHaveClass("text-gray-600");
+      const reason = screen.getByText("Reason with status color");
+      expect(reason).toHaveClass("text-red-700");
     });
   });
 });
diff --git a/src/components/dashboard/decision-card.tsx b/src/components/dashboard/decision-card.tsx
index b54e68f..5e34512 100644
--- a/src/components/dashboard/decision-card.tsx
+++ b/src/components/dashboard/decision-card.tsx
@@ -1,17 +1,43 @@
 // ABOUTME: Dashboard card displaying today's training decision.
-// ABOUTME: Shows decision status, icon, and reason prominently.
+// ABOUTME: Shows decision status, icon, and reason with color-coded backgrounds.
 import type { Decision } from "@/types";
 
 interface DecisionCardProps {
   decision: Decision;
 }
 
+function getStatusColors(status: Decision["status"]): {
+  background: string;
+  text: string;
+} {
+  switch (status) {
+    case "REST":
+      return { background: "bg-red-100 border-red-300", text: "text-red-700" };
+    case "GENTLE":
+    case "LIGHT":
+    case "REDUCED":
+      return {
+        background: "bg-yellow-100 border-yellow-300",
+        text: "text-yellow-700",
+      };
+    case "TRAIN":
+      return {
+        background: "bg-green-100 border-green-300",
+        text: "text-green-700",
+      };
+    default:
+      return { background: "border", text: "text-gray-600" };
+  }
+}
+
 export function DecisionCard({ decision }: DecisionCardProps) {
+  const colors = getStatusColors(decision.status);
+
   return (
-    <div className="rounded-lg border p-6">
+    <div className={`rounded-lg p-6 ${colors.background}`}>
       <div className="text-4xl mb-2">{decision.icon}</div>
       <h2 className="text-2xl font-bold">{decision.status}</h2>
-      <p className="text-gray-600">{decision.reason}</p>
+      <p className={colors.text}>{decision.reason}</p>
     </div>
   );
 }